Big Hit is known for being secretive about their trainees (for example, they kept BTS' V hidden until debut). While many of the former male trainees have debuted (Topp Dogg Kidoh, Boys Republic Suwoong, KNK Seungjun and Inseong), people don't really seem to know about BigHit's former female trainees. The ones currently known are:

SinB and Eunha knew each other before being part of Big Hit. SouMu got SinB first and Eunha was the last one to join Gfriend (after one of the members left) because Big Hit had no intentions of debut a GG any time soon.